TOWSON, Md. — A grand jury on Monday returned a 16-count manslaughter indictment against the engineer of the Conrail locomotive that collided with a passenger train and killed 16 people in the worst accident in Amtrak's history.

Ricky L. Gates of Essex operated his unit of three Conrail locomotives in a "grossly negligent manner" in what amounted to a "wanton or reckless disregard for human life," according to the Baltimore County grand jury.

The Jan. 4 accident near Chase, Md., also injured 175 people.

Failed to Stop Locomotives

Investigators have said that Gates, 32, failed to slow or stop the locomotives at signals before they jumped through a switch and into the path of the 600-passenger Amtrak train.

Baltimore County State's Atty. Sandra A. O'Connor, who announced the indictment, said Gates had "run a stop signal."

No charges were brought against Conrail brakeman Edward Cromwell.

Gates was charged with manslaughter by locomotive, a misdemeanor, with each count carrying a maximum penalty of five years in prison and a $1,000 fine.

The manslaughter charges were the most serious Gates could have faced, O'Connor said.

Gates' bail was set at $50,000, as the state had recommended. He was unable to post the bond and was to spend the night at a county lockup pending a bail review hearing today before a district judge, said E. Jay Miller, a police spokesman.

Gates appeared at a news conference several hours after the indictment was announced but refused to answer questions.

His public defender, Thomas J. Saunders, said that his client would plead not guilty.

The National Transportation Safety Board is expected to release its findings into the crash late this summer.

Both Resigned

Gates and Cromwell resigned from Conrail last week before the completion of disciplinary hearings. They had been suspended without pay after the accident.

Traces of marijuana and its byproducts were found in blood and urine samples taken from Gates and Cromwell several hours after the accident, but federal officials have questioned the validity of the tests.

On Friday, Gates pleaded guilty to driving a car while under the influence of alcohol and two other traffic violations stemming from an incident about a month before the crash. He was fined $1,000 and ordered to undergo counseling.